Aortic aneurysm

Abdominal Aortic Aneurysm (AAA)

• Etiology/Pathophysiology
  • Most common true arterial aneurysm.
  • Primary cause: Atherosclerosis, leading to chronic inflammation, elastin degradation, and weakening of the aortic wall.
  • Location: Almost always infrarenal (below the renal arteries), partly due to the absence of vasa vasorum in this segment, making it more susceptible to ischemia.
  • Defined as aortic diameter > 3.0 cm.
• Risk Factors
  • Smoking: Strongest modifiable risk factor.
  • Age > 60-65 years.
  • Male gender (4:1 ratio).
  • Family history.
  • Hypertension.
• Clinical Features
  • Usually asymptomatic and found incidentally.
  • Symptomatic:
    • Pulsatile abdominal mass (buzzword).
    • Dull abdominal or back pain.
  • Rupture Triad (Surgical Emergency):
    • Sudden, severe abdominal or back pain.
    • Hypotension/shock.
    • Pulsatile abdominal mass.
• Diagnostics
  • Screening/Initial Dx: Abdominal ultrasound.
    • USPSTF recommends a one-time screening for men aged 65-75 who have ever smoked.
  • Pre-operative planning/Symptomatic pts: CT angiography is the test of choice for detailed anatomical mapping.
• Treatment
  • Conservative management for aneurysms < 5.5 cm:
    • Smoking cessation.
    • BP control (e.g., beta-blockers).
    • Serial ultrasound monitoring.
  • Surgical Repair: Indicated if:
    • Diameter > 5.5 cm in men or > 5.0 cm in women.
    • Rapid growth (>0.5 cm in 6 months or >1 cm per year).
    • Presence of symptoms or rupture.
  • Options: Open repair or Endovascular Aneurysm Repair (EVAR).

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Thoracic Aortic Aneurysm (TAA)

• Etiology/Pathophysiology
  • Primary cause: Cystic medial necrosis, a degenerative process of the aortic media.
    • It is characterized by the breakdown and loss of the structural components that give the aortic wall its strength and elasticity.
    • This loss of structural elements leads to the formation of small, empty spaces or “cysts” that fill with a basophilic, mucopolysaccharide-rich substance (mucoid material).
  • Associated Conditions:
    • Connective tissue diseases: Marfan syndrome (FBN1 gene mutation) and Ehlers-Danlos syndrome (collagen defects).
    • Bicuspid aortic valve.
    • Tertiary syphilis (obliterative endarteritis of the vasa vasorum) → classic “tree-bark” appearance of the aorta.
  • Location: Most commonly involves the ascending aorta.
• Risk Factors
  • Hypertension.
  • Connective tissue disorders (Marfan, Ehlers-Danlos).
  • Family history.
  • Smoking.
• Clinical Features
  • Mostly asymptomatic.
  • Symptomatic (due to compression of adjacent structures):
    • Chest or back pain.
    • Hoarseness: Compression of the recurrent laryngeal nerve.
    • Dysphagia: Compression of the esophagus.
    • Cough or dyspnea: Compression of the trachea.
  • Rupture/Dissection: Presents as sudden, severe, tearing chest pain radiating to the back.
• Diagnostics
  • Initial/Incidental Finding: Often seen as a widened mediastinum on chest X-ray.
  • Definitive Dx: CT angiography is the gold standard for diagnosis and pre-operative planning.
• Treatment
  • Medical management:
    • Strict BP control, with beta-blockers being first-line to reduce aortic wall shear stress.
    • Activity restriction (e.g., avoiding heavy lifting).
  • Surgical Repair: Indicated if:
    • Diameter > 5.5-6.0 cm for ascending aorta.
    • Diameter > 5.0 cm in patients with Marfan syndrome.
    • Rapid growth.
    • Presence of symptoms or dissection.
  • Options: Open surgical repair or Thoracic Endovascular Aortic Repair (TEVAR).

Feature	Abdominal Aortic Aneurysm (AAA)	Thoracic Aortic Aneurysm (TAA)	Aortic Dissection
Patho	True aneurysm; Wall weakening	True aneurysm; Wall weakening	Intimal tear, false lumen
Location	Infrarenal	Ascending or Descending	Stanford A (Ascending), B (Descending)
#1 Risk Factor	Atherosclerosis (Smoking)	Hypertension / Marfan	Hypertension
Presentation	Usually asymptomatic, pulsatile mass	Usually asymptomatic, compression Sx	Tearing chest pain radiating to back
Key Finding	Pulsatile abdominal mass	Aortic regurgitation murmur	Asymmetric BPs or pulses
Dx	Ultrasound (screening)	CT Angiography (CTA)	CTA (stable), TEE (unstable)
Tx	Repair if >5.5 cm or symptomatic	Repair if >5.5 cm or symptomatic	A: Surgery B: Medical (β-blockers)